428 THE ZOOLOGIST. 



being 0*96 m. At D 1 and D 2 the winter high water-line was 

 marked by a large quantity of small flood rubbish. Both nests 

 were laid on this line, D 1 slightly above, D 2 slightly below, its 

 centre. D 2 was in no danger, being 0*9 m. above bottom level. 

 It is evident from the history of these nests that, in any 

 further observations on the choice of nesting site, distance from 

 the water will have to be considered along with height above 

 water. The D 1 , D 2 nests lead one to expect that flood rubbish, 

 when it is present, controls the tendency to follow the descent 

 of the level of the water. The main point, however, which it is 

 desired to bring out has already been stated, and may here be 

 repeated, that the stereotyped behaviour appropriate to the 

 normal laying period, when the rainfall is small and fairly 

 uniform and the level of the loch is sinking, is not so successful 

 in controlling the situation in the different environmental con- 

 ditions of a later abnormal laying period when the rainfull has 

 increased and the level of the loch is rising. 



VII. — The Law of Territory. 

 Each settlement on the south shore of the Forth has an 

 habitual range which it rarely exceeds. Individual settlements 

 have not been known to trespass on each other's feeding-grounds 

 for the purpose of feeding. It is remarkable that from winter to 

 winter the position and total areas of the several territories 

 show no change, and that the occupants of each territory have 

 a similar routine of activities year after year. It has not been 

 found possible to point to any general or specific variation of 

 behaviour, relative to the environment, by comparing the observa- 

 tions of one year with those of another (1906-1914). All the 

 settlements under observation in the Firth of Forth have, in 

 each case, a refuge which is also the headquarters of the 

 station. In places where the refuge is not resorted to at every 

 high water (neap tides, nocturnal high water) and in localities 

 where no refuge is available or necessary, a certain part of the 

 beach, on the high water-mark, is constantly used in preference 

 to other parts as a resting place during high water, and there- 

 fore may be regarded as the headquarters. In the Forth the 

 territories are well-defined owing to the intervention of broad 

 bands of neutral shore having little food value. The more 



